Microstructural Analysis of Thermally Treated Geopolymer Incorporated with Neodymium

Sanja Knežević; Marija Ivanović; Dalibor Stanković; Danilo Kisić; Snežana Nenadović; Jelena Potočnik; Miloš Nenadović

doi:10.3390/nano13101663

Microstructural Analysis of Thermally Treated Geopolymer Incorporated with Neodymium

Nanomaterials (Basel). 2023 May 18;13(10):1663. doi: 10.3390/nano13101663.

Authors

Sanja Knežević¹, Marija Ivanović¹, Dalibor Stanković², Danilo Kisić³, Snežana Nenadović¹, Jelena Potočnik³, Miloš Nenadović³

Affiliations

¹ Department of Materials, Vinča Institute of Nuclear Sciences, National Institute of the Republic of Serbia, University of Belgrade, Mike Petrović Alasa 12-14, Vinča, 11000 Belgrade, Serbia.
² Faculty of Chemistry, University of Belgrade, Studentski trg 16, 11000 Belgrade, Serbia.
³ Department of Atomics Physics, Vinča Institute of Nuclear Sciences, National Institute of the Republic of Serbia, Mike Petrović Alasa 12-14, Vinča, 11000 Belgrade, Serbia.

Abstract

The following investigation presents the thermal treatment of geopolymer at 300 °C, 600 °C and 900 °C. We investigated what happens to the geopolymer base when incorporated with 1% and 5% of neodymium in the form Nd₂O₃. A total of six samples were synthesized. Geopolymer 1 contained 1% and geopolymer 2 contained 5% Nd₂O₃, and these samples were treated at 300 °C; then, samples geopolymer 3 and geopolymer 4 also had the same percentage composition of Nd₂O₃ and were treated at 600 °C, while samples geopolymer 5 and geopolymer 6were treated at 900 °C. Physical and chemical changes in the aluminosilicate geopolymer matrix were monitored. The incorporation of rare earths into the polymer network of aluminosilicates has been proven to disrupt the basic structure of geopolymers; however, with increased temperatures, these materials show even more unusual properties. Diffuse reflectance infrared Fourier transform (DRIFT) analysis showed that the intensity of the vibrational band decreases with the increase in temperature during thermal treatment, suggesting alterations in the chemical structure of the geopolymers. Transmission electron microscopy (TEM) analysis showed that the diameter of the nanoparticles containing Al₂O₃ is in the range 5-10 nm, while larger crystallites range from 30 to 80 nm. Scanning electron microscopy (SEM) analysis revealed that the temperature of the thermal treatment increases to 300 °C and 600 °C; the porosity of geopolymer increases in the form of the appearance of large pores and cracks in material. X-ray photoelectron spectroscopy (XPS) analysis was used to investigate the surface chemistry of geopolymers, including the chemical composition of the surface, the oxidation state of the elements, and the presence of functional groups. The UV/Vis spectra of the synthesized geopolymers doped with Nd³⁺ show interesting optical properties at 900 °C; the geopolymer matrix completely disintegrates and an amorphous phase with a rare-earth precipitate appears.

Keywords: DRIFT; Nd2O3; SEM; TEM; XPS; geopolymer; rare earth.

Grants and funding

The research was financially supported by the Ministry of Science, Technological Development and Innovation of the Republic of Serbia, contract number: 451-03-47/2023-01/200017, within the scope of the research topic No. 0402305.